Tandem expansible rotary drill bit



Oct. 6, 1953 A. w. KAMMERER TANDEM EXPANSIBLE ROTARY DRILL BIT 5Sheets-Sheet l Filed Jan. 9, 1950 I INVENTOR. Alea/Eze WMMEQE@ T rjeA/ExA. w. KAMMERl-:R 2,654,575

TANDEM EXPANSIBLE ROTARY DRILL BIT 3 Sheets-Sheet 2 TTQA/Ex INVENTOR.Qc/EQ WMMEQER,

Oct. 6, 1953 Filed Jan. 9, 1950 Oct. 6, 1953 A. w. KAMMi-:RER 2,654,575

TANDEM EXPANSIBLE ROTARY DRILL BIT Filed Jan. 9, 1950 5 Sheets-Sheet 3yda. fifa.

larging the diameter of the bore hole to a. considerable extent. Thelower bit B will enlarge the bore hole diameter to an intermediate size,whereas the upper bit A is capable of increasing the size of the borehole to a greater diameter than that produced by the lower bit.Additional Vbits can be mounted in tandem fashion above the existingbore hole, as desired. As disclosed in the drawings, a pilot bit I issecured to the main body II of the lower expansible drill bit B, for thepurpose of cutting a new hole or assist in centering the bit assembly inan existing hole. The cutters i2 of the lower expansible bit are adaptedto form a shoulder E in the formation, and then operate upon suchshoulder in a downward direction to form a bore hole F of increaseddiameter. The cutters I3 of the upper expansible bit A are adapted toform an annular shoulder G in the formation around the larger hole Fproduced by the lower expansible bit cutters I2, and operate upon suchformation shoulder to form a well bore H of still further increaseddiameter.

The lower drill bit B is illustrated and described in my United StatesPatent No. 2,466,991, and in my application for Expansible Drill Bit,Serial No. 43,789, led August 12, 1948. The upper drill bit A isdescribed and claimed per se in my application for Expansible RotaryDrill Bits, Serial No. 137,535, filed January 9, 1950.

The upper end of the lower expansible bit B consists of a drivingmandrel I4 whose upper pin Y I5 is threaded into a box I6 formed at thelower end of the main body I'I of the upper expansible drill bit A. Thislower mandrel I4 includes an upper kelly or drill stem member I8slidably splined to or telescoped within the main body II or" the bit.As specically disclosed in the drawings, the exterior I5 of the kelly ishexagonal in shape, being telescoped within a companion hexagonal socket2s within the body. The mandrel I@ has a limited range of longitudinalmovement within the body I I, by virtue of engagement of an externalshoulder 2I on the kelly I3 with a retainer ring 22 on the upper end ofthe body, which is suitably secured to Vthe latter, as by the use ofwelding material 23.

The lower body l I (see Fig. 7, particularly) has a plurality -ofexpansible parts mounted on it, comprising cutter Y supporting members24 pivotally mounted in body slots 25 onpivot or hinge pins 2B suitablysecured to the body. Each cutter supporting member 24 consists of adepending leg 2'! having a bearing supporting pin 28 inclined inwardlyand downwardly, and on which a' roller side cutter i2 is rotatablymounted. Anti-friction roller and ball bearing elements 29, 30 areplaced between each cutter I2 and bearing pin 28, in order to transmitthe radial and axial thrusts imposed upon the cutter. The ball bearings30 also retain eachcutter I2 on the pin 28, being inserted in placethrough a pasage 3l in the Ybearing pin, which is then clorsed'by a plug32 welded to the pin. The plug or pin 32 depends from the passage 3| andis used torhold the cutters I2 in retracted position, as describedbelow` Each cutter supporting member 24 also includes an upwardlyextending arm 33 against which an elastic o1' compressed coil springexpander 34 bears. This expander is received within a retainer pocket 35in the body I I, and exerts its force against the arm 33, tending toswing it inwardly and thereby urge the cutters I2, on the other side ofthe fulcrum pin 26, in an outward direction. The extent of this outwardmovement is limited by engagement of the cutter supporting member withshoulders 36 of the body on opposite sides of the slots 25, whichshoulders function as stop members.

After the cutters I2 have been expanded outwardly by the expandersprings 3d to the maximum extent, they can be locked in this position bya tubular member 31 of the mandrel I4, which member is piloted in thekelly it. This member 31 is provided with a lock portion 38 movable froman upper position in transverse alignment with recesses 39 formed in thesupporting members 24, permitting retraction of the cutters I2,

to a lower position opposite lugs @t formed on and projecting inwardlyfrom theV supporting member legs 27, preventing retraction of thecutters I2.

The tubular member 31 may be connected in swivel fashion to the kelly I8to permit relative arcuate rotary movement therebetween, which can occurto a slight extent. However, the kelly I8 and tubular member 31 arecoupled together for movement in both directions. rThis is accomplishedby providing an anti-friction thrust bearing 4I between a boss orshoulder i2 on the tubular member 3l and the kelly I3. The shoulder [i2is received Within a socket 43 in the kelly, and has a toroidal raceway44 on its exterior around which a plurality of bearing balls 45 can bedisposed. These balls are also received in an opposed torodal raceway 45in the kelly i8.

The balls 45 are insertable into and between the raceways 44, 46 througha hole 4l extending through the external kelly shoulder 2I andcommunicating with the internal race 45. After the balls have been thusdisposed in positiony the hole is closed by a suitable plug 48 which isprevented from moving outwardly of the kelly by the inner .wall of thesurrounding body I I.

ymember by suitable packing 52j disposed between its boss 42 and thekelly I8.

Because of the swivel connection @.I, the kelly I8 andtubular member 3are caused to move jointly in both directions, but they are free topartake of relative movement with respect to each other.

The mandrel I4 may normally be held in its upper position with respectto the main body II and the supporting members 25 by a helical retractorspring 53 encircling the tubular member 31, with its upper end engagingthe mandrel shoulder 42 and its lower end engaging a spring seat 5e Yatthe lower end of the hexagonal body socket 20. This spring seat 5d alsoserves as an upper bearing guide for the tubular member 31,

f whose lower end is slidable Ywithin a lower bearing guide 55 below thelugsV 48, which guide is integral with or secured to the main body ofthe bit.

The lower drill bit B may also be provided with latch device forretaining the cutters l2 initially in' retracted positions" against theexpansible forces of the springs 34. This device includes a holdingplate 56 secured to the lower end of a central rod 51 projectingupwardly into the tubular rnexnber passage 5|. The holding plate ormember 56 has spaced holes 5t in its outer portion for receiving thelower ends of the ball bearing 'plugs 32. i

When the holding device is disposed over the plugs 32.V the cutterSupporting nernbers 2&1 are prevented from expand-ing under theiniluence of the compressed springs 34. thereby holding the cutters l2in retracted position'. Release or the holding device 'can occurhydraulically through aid of a ball a9, which may be dropped dow-n thedrill string C into engagement with the rod 5l, r which may be placed inthe lower drill bit passage i prior to its disposition in the well bore.

During lowering of the apparatus through the Well bore; the b'all 59 maybe lifted into the larger passage 59 through the kelly pin', for thepurpose of allowing upward now of iluid through the bits B; A and drillpipe C-.

As explained below, when the point in the well bore has' been reached atwhich the rearning operation is to begin, the latch device 5S iseject'e'd hydraulically from the cutter mechanism, allowing the springset to 'eiipand 'and urge the cutters I2 in an outward direction toenlarge the well bore;

, The lower expansible drill bit B will enlarge vthe well bore to 'acertain intermediate diameter. The upper expansible drill bit A 'canenlarge the well bore to a sti-ll greater diameter. As shown mostclearly in Fig, 6, the main body il of this upper bit is secured to themandrel it of the lower bit B by threading the upper body boit l ontothe mandrel pin I5. upper tubular inandrel 68 is piloted within theupper body and has its upper end formed as a threaded @l which 'can bescrewed into a sub '2 that cbnstit'ute's the lowermos't portion of thestring of drill pipe C. The upper mandrel Gli includes an upper kelly ordrill stem member 63 sliilably splin'ed to the main bo'dy of the bit, asby forming the exterior .G4 of the kelly of hexagonal 'shape andproviding a 'corresponding hexagonal ysocket E5 in the b'o'tly. Themandrel 50 has a predetermined rang 'of longitudinal movement Within thebody, its lipward movement being limited b'y engagement of an externalshoulder S6 on 'the kelly with the retainer ring tl at the' up'per endof the body il, the ring being suitably secured to the latter, 'as byuse of welding material eil.

rihe Aupper body il is provided with fa longitudinal transverse slot 59'extending through it, in Ywhich a 'pair of opposed cutter slipportlngmembers iii are disposed. These 'cutter sup ort'- ing members have'their upper 'ends mounted fon pivot or hinge pins l! extending acrossthe holly slot and suitably secured to the body. 'The cutter .supportingmembers or legs lil 'depend from these hinge pins to a substantialextent, each having a lower bearing supporting .pin l2 'on which a 'sidecutter i3 is rotatably lilou-nte"d.v Antieriction roller and ballbearing lelements la., 'it `-are disposed between each bea-ringsupporting pin l2 and cutter i3. to transmit the radial Tand axialbearing loads therebetween, the ball bearing-elewhit-h closed by asuitable plug 11B welded, or therwise suitably attached, :to the pini.The plugs F116depending'` rm'trie bearing pins .l2 :can be availed offor holding the supporting l'egs land Ycutters t3 Qin retractedposition, as described iielowl.

The `ipp'ositely vdisposed bearing' supporting rnenbers and theircutters :may ioocupy retracted .positions substarnially entirely withinthe con- -nes .of the upper tbod-y H. They may be eX- 'apanded mrtwardlyloaf the body to :a larger eiec'tive 'diameter 'than the maximumVrearning diameter of the cutters i2 fof the lower bit B. expand- .i-ngtheV upper cutters It, their supporting legs vlll Yare swung outwardlyabout the hinge ,pins ll to :a predeterminedezitent. v"The .device forexpand- 'iing the upper vcmters `includes a lower tubular 'member il;forming part :of the upper mand-rel "60, and .piloted within a lowersocket .78 in the kelly 263. The' kelly 6i3 andlower tubular member 153`are assernbled together for joint longitudinal movement through aswivel connection T9 that is substantially the saine as `the swivelconnection '4l between the lower kelly I8 and lower tubular member .31.This connection le enables the :upper kelly 6B and tubular member 'iltofsrii-ft angularly with respect Yto one another,y but vcouples Y.therntogether for conjoint longitudinal movement in both 'directions Thetubular member T1 `ext1=.r'1':l's` downwardly through a guide washer andstop elementilb, resting upon a 'shoulder iSl formed on the body.y Thiswasher initially is disposed :below the lower end of the kelly t3. so asto allow the kelly 4and tubular member ll to be rnoved downwardly; for`the purpose vof holding the upper cutters i3 and their supportingmembers l0 ill an outward position. :in addition, the kelly -63 andtubular member il lresisst inward increment 'of the cutters i3 fro-rntheir outward position; and, under some conditions of `:usage or theediiipm'ent, can actually shift `tlf-1e `cutters i3 to their outwardlyexpanded posi'- 'tion. The tubular meinberll is also slidable in valower guide 82 integral with the body, and forming a support for 'thetubular in'ember l?, to rresist ,its lateral movement; The lower end othe tubular vmember is also slidable in the body Ybox l5; communicatingwith the passage 50 in the lower mandrel i8.

The tubular member' 'I1 of 'the mandrel 'et also vhas a cup=shapedthrust head 83 intermediate .the upper and lewer guides Bt, E25 providedwith a depending skirt 811 terminating above a thrust block 85 slid'abealong `the exterior of 'the tubular member ll below its skirt 84. 'Iheblock S5 has longitudinal slots 8S on opposite sides of the ina'ndrel inalignment with the cutter supporting Alegs la7 to carry a pin 8l onleach side ofthe mandrel 'on which the upper ends of inclined thrustlinks 8B are pivo'ted. The lpwer end of each link is attached t'o thecutter supporting member I0 by means of fa -lowei` pin .89, at a point'which is intermediate the hinge pin Il and butter i3;

The upper `cutters 'i3 may b'e expanded outwardly upon v`downwardmovement of the drol with respeet te the body Il, which causes the lowerend of the skirt B4 to engage the bl l; 85; shifting the latterdownwardly and swinging the legs '10 outwardly about their hinge pinsli, through the agency of the thrust links 8u. AIf 'desireety outwardexpansion 'of the upper cutters 13 and-their supporting legs' vlil maybe accompli-shed by a helical compression spring 90s disposed with@ inthe skirt 84 and bearing at its upper lend 'upon 7 the head 83 and atits lower end 'upon the thrust block 85. It is evident that this spring90 tends to urge the thrust block 85 downwardly and the legsl in anoutward direction.

The upper cutters I3 may be releasably locked in retracted position by aholding device, to insure the downward passage of the bit assemblage Athrough the casing, and the well bore below the casing, to the desiredpoint at which the hole enlarging operation is to commence. This holdingdevice may include a rod or eye element il! for each cutter threadedinto the tubular member ll, and having a hole e2 receiving the lower endof the ball retaining plug 16. These elements 9| will prevent outwardexpansion of the cutters I3 until the elements are moved downwardly fromthe plugs 16, as by moving the tubular mandrel 6E) downwardly withrespect to the body I1. The lower end of the mandrel skirt 84 isdisposed a suflicient distance above the thrust block 85, when thecutters I3 are in their initial retracted position, to insure thedownward removal of the lock or latch elements 9| from the plugs 'I5before the skirt 84 can engage the thrust block S5. Without suchrelative positioning of the parts, it may be difficult, if notimposssible, to unlatch the cutters I3, since prior engagement of theskirt with the thrust block would preclude further downward movement ofthe mandrel @El within the upper body Il.

As noted above, the upper mandrel 50 is slidable in the threaded box I6at the lower end of the bit body I1, leakage around the exterior of themandrel being prevented by a suitable side seal 93 in a box groove 94slidably engageable with the exterior of the tubular mandrel.Accordingly, the iiuid pumped down the drill pipe C can pass through theupper kelly passage 95 and the tubular mandrel 'passage Q5, fordischarge into the lower kelly passage 50 and into the lower tubularmember 3l, for the purpose of releasing the lower latch member 56, andthereafter discharging into the well bore to flush the cuttings to thetop of the well bore.

The depending leg portions 2l of the lower cutter supporting members 24are of such length as to enable the cutters I2 to be expanded laterallyto a predetermined maximum diameter, in order to enlarge the well boreto an intermediate size F. The upper cutter supporting members or legs'IQ are substantially longer than the lower legs 2l, to enable thecutter elements I3 to be swung outwardly or expanded to a greatereffective diameter than the lower cutters I2, in order to obtain a stillfurther enlargement H of the bore hole diameter. The extent ofexpansions of the respective upper and lower cutters I3, I2 is properlyselected to insure the eiective operation of the drill bit apparatus inultimately increasing the diameter of the bore hole to the requiredamount.

The drill bit apparatus is assembled with the upper and lower cuttersI3, I2 in retracted positions, in the manner illustrated in Fig. 1,'andwith the upper mandrel pin 6I threaded onto the lower end of the drillpipe C. The upper and lower latches SI, yS are in place, in order tolock the cutters intheir respective retracted positions. Y 1

rihe apparatus is lowered through the well casing (not shown) until itreaches the location in the well bore at which the hole enlargingYoperation is to take place, which may be above the bottom of apreviously drilled hole below the casing shoe (not shown). When thispoint is reached, the tandem drill bits A, B are rotated at the properspeed without imposing any downward weight upon them. The pumps at thetop of the well bore are started, to impose pressure on the drillingiiuid or mud in the drill pipe C and the bits A, B. The pressure acts onthe ball 59 in the lower bit B (which may have been previously insertedin the bit), this ball functioning as a piston and causing the stem 5land locking plate 55 to be shifted downwardly and ejected from the lowerbit. Removal of the locking plate 56 frees the lower cutters I2 andtheir supporting members 24 from restraint and allows the compressedsprings 3d to expand, shifting the arms 33 inwardly and the legs 21 andcutters l2 in an outward direction. With the removal of the latchingdevice, circulating fluid can pass outwardly through the lower nozzleportion 31a of the lower mandrel 3l, in order to wash the cuttings fromthe well bore and circulate them around the drill pipe C to the top ofthe hole.

Rotation of the bit assembly continues, without imposing drilling weighton the apparatus, until the lower cutters I2 form a shoulder E in thewell bore, the cutters being expanded to their maximum extent. Afterthis occurs, the drill string C may be shifted downwardly, which willshift the upper mandrel 60 and its tubular member 'l1 downwardly withinthe upper bit body I'I, the latch elements 9| being moved downwardlyfrom the upper plugs '16, releasing the upper cutters I3 for outwardexpansion. However, the outer surfaces 10c of the legs 'I0 will merelymove outwardly into engagement with the wall of the hole D, since suchsurfaces initially project slightly beyond the cutters I3. Inasmuch asthe cutters I3 cannot be expanded any further, at this time, because ofthe confiring action of the small diameter bore hole E, continueddownward movement of the drill string will then shift the entire upperbit A in a downward direction, sliding the legs 'I0 along the wall ofthe hole. As such downward movement occurs, the lower mandrel I4, whichis rigidly secured to the upper body I1, is'moved downwardly within thelower body II to a position limited by engagement of the lower end ofthe kelly I8 with the lower guide washer 5d. Such downward movement ofthe lower mandrel positions the lower lock element 38 within andopposite the lower lugs 49, forming a positive stop or abutmentprecluding inward movement of the lower cutters l2 from their outwardlyexpanded position.

Rotation of the drill pipe C and cutters continues, the cutters I2enlarging the hole to a greater diameter F by operating upongtheformation shoulder E. As drilling proceeds, the upper legsV 'I0 andcutters I3 will reach the enlarged hole portion F, whereupon they canexpand outwardly, the cutters I3 engaging the enlarged hole wall, andthen extending outwardly beyond the leg surfaces lila.

Rotation of the drill pipe C and the tool as-v semblage A, Blmay thencontinue, the upper spring urging the thrust member 85 dowm wardly alongthe mandrel '11, and, through the links 88V, urging the upper cuttersupporting legs 1l) and cutters I3 in an outward direction, allowing theupper cutters to form an upper shoulder G in the well bore having anoutside diameter H substantially'greater than the outside diameter F ofthe lower shoulder E. v The f 2,8555525 9 10 r, t spring so can .shift.the `cutters la outwardly to its body I l downwardly, and to aposition` in the extent determined by engagement f tli which the lookelement 38is"`disposed withiniarid tnrnet block a .with tnelower'guldes2 in the in alignment lYs/iththe lower lueel. Ezpansion upper body.Thereafter, the "imposition of 0f the upler ll'lflertl ,I3 'een thenProceed, after down Weight .on the drill pipe vC and .upper man; 5 theenlarged bore is reached, by moving'tlie drel so will ehi-ft the latterdownwerulywltriin upper mandrel downwardly within the Vupper the upperbody I8, untilthe lo'wer'end of the body i7 to the extent limited' byengagement of kelly 63 engages the upper 4guide and stop wash'- thelower yend of .the 'kelly v63' with the upper er 80. When suchengagement'occus, the lw uide Washer Ml er end of the mandrel skirt84'is preferably `po- 1g' In Figs'l and 2, a tandem arrangement ofsitioned immediately above and closely adjacent drill bits is disclsed,'which a le'reViOllSly the thrust block 85, to preclude any substantialdrilled hole D can -b enlarged in tWO Stagesinward shifting of thecutters I3 from their If desired, llOle enlargement een take' pleCe inmaximum expanded position, three or 'more stages by incorporating olleor With the lower mandrelM fully .telescoped mre eXpansible ,dri-ll bitsin the assemblage. downwarmy within the lower body '1|, and with As'illustrated in Eig. 8, the' upper pin "leef a the upper mandrel v6|)fully telescoped` downlower .drill bit B iS threadedv into the lowerbOdY wardly with the upper body I1, the dri-11mg box Mld of anYintermediate drill bit Ba, which weight is transmitted from therespective mar'lmay belofthesame general design aS the lower d relsdirectly .to their corresponding bodiesfand drill bit B. `Theintermediate mandrel Ma is from such bodies to the cutter supportingmem-v threaded into the lower box I6 of an upper drill bers 2 4, 1,0 andthe cutters l2, I3. The tubular bit A', whichl may bje ,of the samedesign as the meinbere 77, 3 1 themselves are relieved of any upperdrill bit shown in. Figs. 1 and 2. The up; 0f the .drilling Weight.Rotation vof the drill bit per mandrel pin ,6| gf the upper bit is thenasemblage takes place, .with the .proper @111mg 25 threadedly secured tothe lower end of the drill weight imposed upon lthe sets vof cutters,the pipe C- lower cutters I2 enlarging vthe well bore to' an The.intermediate bit mandrel Ma extends intermediate diameter and the uppercutters slidabl'y into the lower box I D of its associated '3 te thedesired nal diameter H, that is subbody Url, leakage around the mandrelbeing Sienielly greater than the intermediate diamef 3G prevented byafsutable side seal 93a` disposed in ter.v During the drillingoperation, circulation va bOX glQQle .94d- Y'lllli4 intermediate.mandrel uid is pumped downwardly through the bitsv ld i5 also providedwith looking elements 9m A, B, in order to flushthe cuttings .to the.top'of threaded into it and Ahauling holes 92a receiving the noletlleball retaining plugs .32a depending from the After the holeenlargingoperatlon has been 35 intermediate bearing supporting members24a. Completed, 0r the drill ,bits have betonte .worm The @utters l2 ofthe lower blt B are arranged it is merely neeeSSery lle. elevate .thedrill pipel to expand outwardly to a predetermined maxl- C? Which Willreiee the upper mandrel within mum diameter in order to accomplish thefirst the upper body Il; and allow the upper 4cutters stage .of holeenlargement. The cutters 12a of .3 te be retracted The upper .mandrellanee" 4o the intermediate bit Bu may be mounted on longer 66 engagesthe upperv retainer ring .61, toA trans supporting lees. 31a than thelower bit, so that mit the upper Pulling effort tel the upper body theirSprings Illu may sluit such .cutters out-V ll Continued upwardmovementfthen eleyatesv Wardly to aereater .extent'than thel lower,cutters the lower mandrel l!! Within the'lower body H, 12,399 preduee'allole of a larger diameter K than end.- reiSeS the 190k member '3,3apoye the sup:-L 45' that df the lower euttera The .supporting legeYinning member lugs 40, which will allow the' 1.51 ,et tile upperbita maybe ,of suon length as IQW-er @utters l2 and ,their.supportine` members'to enable A@bern to be erung outwardly to a 2e to be retracted. Suchlatter relative eletta-t,- greater extenttnan the intermediate cuttersliga, lng movement mel he eeeieifed: by lheretraotor and form acorrespondingly larger diameter spring 53, although this spring ,neednot beeme; 5g hole t o heele@ in the `bit atan, il desired,rnernultiplelandenl arrangement of drill bits When the drillbitaeeenlblaee erle-passes; up: illustrate Fier berlin in the Well boreWaren 'Within' the easing-"Shea thelatter with el, af @geput-,tersrurale looted iure: gages the upper-cutter"supprtiligwmmbers 19 tractdposition.` n .the 'two stage bit as*-n and forces them inwardly to aretracted posi- 5:5: semplag-e,- tne pumps can be started when the ton-Similarly, the thee''eiieegesAA ill-flower location `has vbeen reached.at which the hole Geiler ,Sllplofing members ?.5 'aldf fPllC'eS' the@enlarging .operation lato occur, to release vthe nWer'dlYtOrelireleted'ljositolr'ille elllfllfe Wegner," lowerY latch from itsassociated cutter sup-V nsm bemg @lemmi-d m, u?? Wencafslrg: Wll-h t' QportingY membersll, allowing the" lower springs Cutter Supp-Ortig memle79' Mifune til? W .elA to urge the cuttersV l-zoutwardly, while thegaldwu casmg lilltll me 1599 gif til-9 bitsarelbeirlgfr'otatd'to formthelower formaf. tionsho'ulder'P This' shoulder prevents theflower'Fh-euppr S-'prmggqfm'gy-b'? pnntgd- 11u11 bodjlilifrommvingdownwardly'to any further tubular member head g3 originallylspose'l a i l 1f u jacent the thrust member' {8,5} when'the cutters65e, GL? e ,btn- 'QI dllf .919e C.,1 [3T-*and their supporting members'1g* are'in `e3- tlfllwreq gq-nwardly S 31 ,g the EDP?? tractedlthe'fltowelf c tv Inanrlr '60 d have' been Vexrande-d out'wa dl slidingalone tner'erm'atiee all. .tile e: per bit parte moveas e llnitin e,devint/.arq

rection. to s hift-the-lower melidil 1l 'mediate springs 34 to urge theintermediate cutters lia outwardly.

Y Continued downward movement then slides the upper bit A andintermediate bit Ba downwardly along the formation wall D, to shift thelower mandrel I4 downwardly within the lower body II to a position inwhich the mandrel lock 38 is disposed within the cutter supporting lugs4U, as determined by abutting of the lower end of the lower kelly i8with the guide washer 54. As the rotation of the drill pipe C and bitapparatus proceeds, the proper drilling weight is imposed, to cause thelower cutters i2 to drill away the hole by operating upon its associatedformation shoulder and produce the larger hole diameter P. While suchdrilling proceeds, the intermediate and upper cutter supporting members24a., 'l slide along the wall of the smallest diameter hole D, the upperand intermediate cutters I3, I2a being disposed inwardly of theoutermost portions of their associated cutter supports '18, 24a. Theupper and intermediate drill bits A, Ba merely move downwardly as aunit, their cutters being incapable of expanding outwardly to anyappreciable extent by the confining wall of the hole D. Y

As drilling by the lower cutters I2 proceeds, the intermediate cutterslZa eventually reach the enlarged well bore P produced by the lowercutters, whereupon the intermediate expansion springs 34a can operateand urge these cutters IZd outwardly and into engagement with the wallof the larger hole P. The drill pipe C and tool assemblage can then berotated, the intermediate cutters 52a, which n-ow project outwardlybeyond the outermost portions of their supporting member 2da, digginginto the wall of the enlarged hole P and forming a shoulder therein of acertain predetermined diameter Q, as limited by engagement of the cuttersupporting members 24a with the body shoulder 36a on the body I Ic. Withthis shoulder formed, the drill pipe C and upper drill bit A can bemoved downwardly as a unit, the upper supporting legs 'I merely slidingalong the wall of the smallest hole D. This downward movement carriesthe intermediate mandrel Illa downwardly with it to shift its lockmember 38d within the lock lugs 4ta, thereby precluding retraction ofthe intermediate cutters lZa from their outwardly expanded position.

Drilling weight may be imposed on the bit assemblage, the lower cuttersI2 producing the larger hole P, and the intermediate cutters I2a thehole Q of still greater diameter.

As drilling proceeds, the upper cutter supporting legs li! will move outof the small diameter hole D, allowing the spring 90, or the head 33, ifa spring is not used, to engage the thrust block 85 and shift itdownwardly, forcing the legs 'i6 and upper cutters I3 outwardly againstthe wall of the enlarged hole Q and forming an annular shoulder beyondthe diameter of the enlarged hole Q. When the upper cutters I3 have beenexpanded outwardly to their maximum extent, the upper mandrel '50 isshifted downwardly within the upper body Il, until the lower end of thekelly t3 engages the guide element 80, whereupon drilling weight can beimposed on the cutters i3 to urge them downwardly against the formationshoulder to produce the desired maximum diameter hole R.

When all three sets of cutters have been expanded outwardly, the bit maybe rotated at the desired speed, with the proper drilling weight imposedon the cutters, the hole being enlarged in step "fashion from itsdiameter D, through the diameters P and Q, to the final diameter'R. Thatis, the lower'cutters l2 perform the rst stage of hole enlarging,` theintermediate cutters I2 the second stage, and the upper cutters 3 thethird stage, as the sets of cutters operate upon their respectiveformation shoulders and cut such shoulders progressively away in adownward direction. When the drill bit assemblage has performed itsoperati-on of enlarging the hole, it need merely be elevated through thewell bore and casing, the cutters being retracted by the casing as theirrespective supporting members enter the casing shoe.

Additional expansibleV bits could be connected in tandem, if desired,within practical limits, to accomplish the desired hole enlargement instages.

It is apparent that a tandem arrangement of drill bits has beenprovided, that is capable of enlarging a hole to a considerably greaterdiameter.,

The use of toothed types of roller cutters enables hole enlargement to asubstantial extent to be accomplished in hard formations. With suchtandem arrangement of drill bits, a single round trip into the well borewill su'ice for greatly enlarging the hole and along an extended lengthof the hole, thereby saving considerable rig time and-expense, byavoiding the necessity for making individual trips into the hole withindividual expansible bits to accomplish a step-by-step increase in thewell bore diameter.

With the telescopic arrangement of bits, assurance is had that each setof bit cutters is expanded and locked outwardly to its full reamingdiameter, in order that each bit will perform its proper share of thedrilling operation. It is simply necessary to attach the drill bits toone another, and in the desired number, each drill bit being a full andcomplete mechanism in and of itself. The outward expansion of thecuttersy of an upper bit is dependent upon the prior outward expansionof the cutters of a lower bit. The cutters are expanded outwardly in anupward sequence, and are locked outwardly, to prevent their inwardretraction, by the telescopic movement of the tubular mandrels withintheir respective bodies.

The hole enlarging operation can commence off bottom in a previouslydrilled holes or the tandem assemblage can be used in conjunction with acentral bit le for the purpose of drilling a new hole and enlarging itin stages at one and the same time. Y

The inventor claims:

1. In rotary drill bit apparatus: a lower drill bit body; a lowermandrel slidably splined to said body; a lower supporting member mountedon said body for lateral outward movement with respect to said body; alower cutter on said member; means for expanding said member and cutteroutwardly of said body; an upper bit body securedV to the upper end ofsaid lower mandrel; an upper mandrel slidably splined to said upperbody; an upper supporting member mounted on said upper body for lateraloutward movement with respect to said upper body; an upper cutter onsaid upper supporting member; means for expanding said upper member andupper cutter outwardly of said upper body to a greater extent than saidlower cutter; said upper cutter being disposed entirely inwardly of theoutermost surface of said upper Ysupporting member until said u ppersupporting member has been expanded partially outwardly, whereby saidupper cutter isi amiante 1:3 prevented `from penetrating the l'formation`'until it has been lowered into `the enlarged Ibore-produced by thelower cutter.

2. In `rotary drill bit apparatus: a ilo-wer bit having a lower body; alower supporting member mounted on said body .for lateral outwardmovement with respect 'to `said body; a lowercutteron said member; meansfor expanding said member and cutter outwardly of said body; an-upperibit secured to the upper end vof lsaid lower bit, said upper bithaving a body; an upper supporting member mounted Aon said `upper rbitbody for lateral outward movement -with respect to said upper body; anupper'cutter onsaid upper ymember; lmeans'forexpanding-said-rupperfmember and upper-cutter 'outwardly -of rsaid upperbody to a rgreater extent thansaid lowervcutter; said upper cutter beingdisposed Aentirely inwardly of the outermost surface of saidvuppersupporting mem- 'ber until said upper supporting memberhas been expandedpartiallyoutwardly;whereby-said upper cutteris prevented frompenetratingthe Vformation until it has been'lowered into the enlarged lboreproduced by thelower cutter.

3. In rotarydrill-bit apparatus: af-lowerdrill bit body; a lower-mandrelslidably spline'dtovsaid tbody; a lower-supporting-member lmounted-onsaid body for lateral outward movement with respect to said body;#aflowercutter'on said supporting member; -means'forexpanding saidsupporting Vmember and icutter outwardly of said body; meansl on saidmandrel for-'preventing substantial `inward movement of said :supporting-member and cutter v`from their outward expanded-position upon downwardtelescopic movement of said mandrel'in said body; an upper bit bodysecured to the upper endof'said lower mandrol; an uppermandrelslidablysplined to'said upper body; an vupper supporting -membervmounted on said upperv body icrlateralroutward movement with respect-to f said upper 'l body; f an upper cutterY on said 'upper supportingmember; means for expandingsaid upper supporting member and upperfcutteroutwardlyofsaidupper 'body vto a greater 'extent than saidlowervsupporting member and cuttermeansion saidupper mandrel forpreventing substantial yinward movement of said `upper ASupportingmember and `upper cutter from-theiroutward expanded posi- 'tion upondownward telescopic-'movement'oisaid upper mandrel :in said -`uppertbody; said upper cutter being disposed entirely inwardlyof Vtheoutermostsurfaceosaidaupper supporting member until said uppersupporting member has been expandedl partially outwardly,wherebyfaidjupper cutter is preventedI frompenetrating-,the formationuntil it has been lowered linto the enlarged bore produced by thelowercutter.

Qi. In rotary `drill bit-apparatus: a lowerdrill `bit'body; a lowerymandrelfslfidably splined'wto Asaid body; a lower supporting membermounted on 'said body for lateral outward movement with -re- 'spect-vtov said-body; alowerfcutter onY saidsupporting member;- -mea-ns-forexpanding said supporting member and cutter outwardly of said body;means on said mandrel for preventing substantial inward movement of saidsupporting member and cutter from their outward expanded position upondownward telescopic movement of said mandrel in said body; an upper bitbody secured to the upper end of said lower mandrel; an upper mandrelslidably splinded to said upper body; an upper supporting member mountedon said upper body for lateral outward movement with respect to saidupper body; an upper cutter Vori said upper .supporting member.; -meaiisfor expanding said upper :supporting .member ,and vupper cutteroutwardly of said upper body to a greater extent than .said ,lowersupporting mem.- ber andcutter; means on saiduppermandrel for preventingsubstantial inward Amovementof said upper supporting lmemberand upper`cutter from their -outward `expanded vposition .upon .downwardtelescopic movement of .said .upper mandrel lin said ,upper body; saiduupper cutter being `disposed entirely .inwardly of thel outermostsurface of said upper supporting .member until said upper Asupportingmember z-has been expanded partially outwardly, Ywhereby said Y.upper.cutter is -prevented from lpenetrating the formation until it has :beenlowered into vthe enlargedfbore produced .bythe-lower cutterrandlockmeans re,- leasable lby .said upper Imandrel .upon -its .downward`telescopic movementin said upperbody "for holdingy said uppersupporting member `and'uppler cutterinitially inlretracted position.

f5. In rotary drilllbitapparatus: a lowerdrill bit body; a lowerfrmandrel .slidably splined .to said body; a'lowersupportingmembermounted on saidv body vfor lateral outwardmovement with respect -to saidbody; a Alower `,cutter on said suporting .member; fmeans .forA,expanding said supporting member and cutter outwardly of said body;means on ysaidmandrel iforipreventing substantial inwardmovementiofsai-d supporting 'member land cutter `from,theiroutwardexpanded position upon downwardtelescopic movement `rof saidmandrel in said bodyyan-upperfbit bod-yv se- -curedto the upper enclofsaid loWermandreI; 'an upper mandrel slidablyspl-ined `,tosaid upperbody; van upper `supportingmen1ber.mounted on said upper body`forwlateral :outwardfzmovement lwith respect -to'- said upper 2body;lan:upper cutter on said upper supporting member; meansforexpendingsaidupper supporting member andupper cutter outwardly of said upperzbodytoa greater extent than said lower supporti-ng .member and cutter; means-on .said upper-mandrel forf-preventing substantial :inward movement of4said upper supporting.member-fand. upperA cutter from their outwardexpandedl -position upon.- downward `telescopic `movement of .said-upper Y mandrel in said upper body; v upperlockfmeans releasable-'bysaid upper mandrel; upon vits downwardltelescopic movement in said'upperbody --for :holding said upper supporting vvmember and yupper cutterinitially in retracted position; and lower vlock ymeans 4for releasablyholdinglsaid rlower .cutter supportingmember and .lower cutterinitially-iin I lretracted position, :whereb-y-saidflower.lock means is--rst released fto-aenable said` lower'supporting Lmember and llowercutter to f be expanded outwardly to providea shoulder-V-in--a-bore.hole for ,stopping downward movement .of.said1low.er Lbit body to permitdownward telescopingfmovement oisaidzupper mandrel .inlsaid upper lbodytoire- `lease said upperlock means.

`A6.1m rotary drillbitapparatus: .-adilower drill bit-body; a lowermandrel slidabl-y splined to said body; a lower supporting membermounted on said body for lateral outward movement with respect to saidbody; a lower cutter on said supporting member; means for expanding saidsup-,- porting member and cutter outwardly of said body; means on saidmandrel for preventing sube stantial inward movement of said supportingmember and cutter from their outward expanded position upon downwardtelescopic movement of said mandrel in said body; an upper bit bodysecured to the upper end of said lower mandrel;

an upper mandrel slidably splined to said upper body; an uppersupporting member mounted on said upper body for lateral outwardmovement with respect to said upper body; an upper cutter on said uppersupporting member; means for expanding said upper supporting member andupper cutter outwardly of said upper body to a greater extent than saidlower supporting member and cutter; means on said upper mandrel forpreventing substantial inward movement of said upper supporting memberand upper cutter from their outward expanded position upon downwardtelescopic movement of said upper mandrel in said upper body; lock meansreleasable by said upper mandrel upon its downward telescopic movementin said upper body for holding said upper supporting member and uppercutter initially in retracted position; and lock means for releasablyholding said lower cutter supporting member and lower cutter initiallyin retracted position; said upper cutter being disposed inwardly of theoutermost surface of said upper supporting member, until said uppersupporting member has been expanded partially outwardly, whereby saidupper cutter is prevented from penetrating the formation until it hasbeen lowered into the enlarged bore produced by the lower cutter,

7. In rotary drill bit apparatus: a lower drill bit body; a lowermandrel slidably splined to said body; a lower supporting member mountedon said body for lateral outward movement with respect to said body; alower cutter on said supporting member; means for expanding saidsupporting member and cutter outwardly of said body; means on saidmandrel for preventing substantial inward movement of said supporting lmember and cutter from their outward expanded position upon downwardtelescopic movement of :said mandrel in said body; an upper bit bodysecured to the upper end of said lower mandrel; an upper mandrelslidably splined to said upper bit body; an upper supporting membermounted on said upper body for lateral outward movement with respect tosaid upper body; an upper cutter on said upper supporting member; meansfor expanding said upper supporting member and upper cutter outwardly ofsaid upper body to a greater extent than said lower supporting memberand lower cutter; means on said upper mandrel for preventing substantialinward movement or said upper supporting member and upper cutter fromtheir outward expanded position upon downward telescopic movement ofsaid upper mandrel in said upper body; upper lock means releasable bysaid upper mandrel upon its downward telescopic movement in said upperbody for holding said upper supporting member and upper cutter initiallyin retracted position; said upper and lower drill bit bodies andmandrels having intercommunicating fluid passages therein; and lowerlock means releasable by fluid pumped through said passages for holdingsaid lower cutter supporting member and lower cutter initially inretracted position, whereby said lower lock means is first released byfluid pumped through said passages to enable said lower cuttersupporting member and lower cutter to be expanded outwardly to provide ashoulder in a bore hole for stopping downward movement of said lower bitbody to permit downward telescoping movement of said upper mandrel insaid upper body to release said upper lock means.

8. In rotary drill bit apparatus: a lower bit having a lower body; alower supporting member mounted on said body for lateral outwardmovement with respect to said body; a cutter on said member; means forexpanding said member and cutter outwardly of vsaid body; means forlimiting the maximum outward expansion of said member and cutter; anintermediate bit secured to the upper end of said lower bit, saidintermediate bit having a body; an intermediate supporting membermounted on said intermediate bit body for lateral outward movement withrespect to said intermediate body; an intermediate cutter on saidintermediate member; means for expanding said intermediate member andintermediate cutter outwardly of said intermediate body to a greaterextent than said lower cutter; means for limiting the expansion of saidintermediate member and intermediate cutter to a maximum extent in whichthe cutting path of said intermediate cutter extends outwardly a greaterradial distance than the cutting path of the lower cutter but in whichsaid pathsoverlap; an upper bit secured to the upper end' of saidintermediate bit, said upper bit having a body; an upper supportingmember mounted on said upper bit body for lateral outward movement withrespect to said upper body; an upper cutter on said upper member; meansfor expanding said upper member and upper cutter outwardly of said upperbody to a greater extent than said intermediate cutter, in which thecutting path of said upper cutter is grter than that of saidintermediate cutter but overlaps the path of said intermediate cutter;said intermediate and upper cutters being disposed entirely inwardly ofthe outermost surfaces of their respective supporting members until saidrespective supporting members have been expanded partially outwardly,whereby said intermediate and lower cutters are prevented frompenetrating the formation until they have been lowered into the enlargedbore produced by the lower cutter.

ARCHER W. KAMNlERER.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 1,152,151 Decker Aug. 31, 1915 1,375,094 Humason Apr. 19, 19211,607,937 Aldrin vNov. 23, 1926 1,640,341 Aldrin Aug. 30, 19272,466,991Y Kammerer Apr. 12, 1949 2,545,037 Kammerer Mar. 13, 1951

